What plant is that?

The mystery plant for June is a perennial with opposite and entire leaves. The flowers are pink to white and have 5 petals and 5 sepals. The sepals are fused into a tube while the petals are separate. The lanceolate leaves are smooth, 3-5” long and 1-2” wide. This plant grows in waste places and is from 18-30” tall.  It blooms from mid - June to late September.  This plant is not native but introduced from Europe.

It’s. . .